Stabilility Flashcards
What’s stable equilibrium?
If the centre of gravity and the centre of buoyancy are no longer perpendicular to each other, and the centre of gravity is below the meta centre of the ship
Righting lever occurs
What’s righting leaver
It’s a created moment known as the righting moment which returns the ship to its original position
What’s a neutral equilibrium
When the vertical position of the centre of gravity and the meta centre over lap , and no righting lever is created during the heel
Which will not bring back the ship to a original upright position
What’s an unstable equilibrium
This is when the vertical position of the centre of gravity is above that of the ships meta centre, creating a negative righting lever
What would happen if the ship does not return to a stable equilibrium and the heel keeps increasing?
The ship will eventually capsize due to the negative lever
How does a ship float ?
Due to a buoyancy , which is the upwards force that the sea exerts on a vessel
What happens when an external force occurs on the ship?
This is when a righting leaver occurs which will bring the ship to an upright position, as long as we are at a stable equilibrium
What’s a LOLL
This is the state of a ship that’s unstable when upright
(Negative meta centric height)
Which therefore takes an angle of heel either port or strbd
How can we correct a ship in a state of LOLL
By lowering the centre of gravity;
- moving weight down
-adding water to ballast tanks
- removing weight
What’s a vessel at risk in a state of LOLL
The ship at risk at capsizing
What is LIST ?
It is the degree that a vessel heels to either port or strbd ,
What causes LIST
By unequal loading on either side of the centre line of vessel
What is examples of LIST on ship ?
-The islands
-loading heavy equipment
- jet or aircraft loading
-floods
-overloading on either port or strbd
What stability documents are there?
-Class book
-carpet plots
-stability and survivability
-stability state board
